Digital rights management (DRM) technology is for protecting the rights and activating safe provision of digital contents by preventing illegal provision of digital contents having the rights. In order to build a DRM system, encryption technology, decoding technology, billing, usage right, and public key infrastructure (PKI) technology are utilized.
However, as various DRM technologies have spread, different DRM technologies have been applied to the contents or terminals, and hence, the user has sometimes failed to use the legally acquired contents in his terminal. Since the terminal conditions are varied depending on the DRM technologies and techniques for mounting the DRM are restricted by the DRM technologies, it is impossible to install a plurality of DRM clients in each terminal. Therefore, a technique for guaranteeing interoperability or compatibility between the DRM systems is required for the user's convenience and benefits.
A conventional DRM interoperability technique is provided to perform interoperability by disclosing the DRM skills between the DRM systems to be interoperated. However, it is not recommended to publicize the DRM technique since the contents free of DRM are easy to reproduce and distribute.